import * as React from 'react';

/**
 * Lets the shell's rails glide open and closed instead of snapping.
 *
 * `react-resizable-panels` stores a layout as `flex-grow` per panel and writes
 * it inline, so mounting or unmounting a rail lands the new widths in a single
 * frame. Nothing about that is animatable from the rail's side — the panel
 * appears already at its final size — but the row's other panels do change an
 * animatable property, and interpolating theirs is enough: while main's
 * `flex-grow` travels, the rail's share of the row grows with it, which reads as
 * the rail sliding open.
 *
 * The transition is armed by an attribute that is present from first render,
 * because a transition can only animate a change to a property that already had
 * a value. Arming it later from an effect is too late: panels register in a
 * layout effect that runs before any parent effect, so the widths are already
 * written by the time a parent could add a class.
 *
 * Two situations must disarm it, and this hook owns both:
 *
 * - **A separator drag.** The pointer is the animation. Interpolating on top of
 *   it adds 200ms of lag to every pixel and re-lays out the hub on frames the
 *   user did not ask for.
 * - **A window resize burst.** Every resize event nudges each panel's grow, so
 *   an armed transition turns a window drag into a rubber-band that trails the
 *   frame behind the cursor.
 *
 * Interpolating width does cost a layout per frame — measured at roughly 22fps
 * on a hub carrying a full `HubTable`, against a single layout for a snap. That
 * is the deliberate trade: the shell reads as connected motion, and the cost is
 * bounded to the 200ms the rail is moving.
 *
 * @see globals.css — the `[data-rail-transition]` rule this arms
 */

/** Matches the sidebar's own width transition, so the shell moves as one. */
declare const RAIL_TRANSITION_MS = 200;
type RailLayoutTransitionProps = {
    elementRef: React.RefObject<HTMLDivElement | null>;
    "data-rail-transition": "armed";
};
/** Spread the result onto the `ResizablePanelGroup` holding the rails. */
declare function useRailLayoutTransition(): RailLayoutTransitionProps;

export { RAIL_TRANSITION_MS, type RailLayoutTransitionProps, useRailLayoutTransition };